A game engine powered by python and panda3d
Descent 3 by Outrage Entertainment
High performance UI layout library in C
3D game engine/framework in C, with Luajit and Python bindings now
A game engine with an emphasis on real-time cutting-edge solutions
2D JavaScript Physics Engine
Zig game engine & graphics toolkit
A modern, cross-platform Quake game engine based on FitzQuake.
GemRB is a portable open-source implementation of the Infinity Engine
Orx: Data-Driven Game Engine
Game engine supporting many 3D/2D formats and graphic effects
SDL based generic 2D game engine
C++ lightweight cross-platform game engine
The multiplayer game engine
A Tile-based Game Engine written in C# mimicing retro consoles.
a UCI chess engine
Spring is a free RTS engine developed for Windows, Linux and Mac OS X.
DOOM / Heretic / Hexen source port with enhanced graphics and UI
Amazon Lumberyard is a free AAA game engine
A cross platform Lua based game engine